Compressional wave delay means



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D. LW ARENBERG Hl COMPRESSIONAL WAVE DELAY MEANS Filed April 2, 1946 atented pr. 25', 195,0

COMPRESSIONAL WAVE DELAY MEANS David L. Arenberg, Rochester, Mass., assignor, by mesne assignments, to the United States of America as represented by the Secretary of War Application April 2, 1946, Serial No. 659,113

(Cl. TIS- 44) 8 Claims. 1 This invention relates to delay means and more particularly to solid delay lines that provide a relatively short time delay.

Supersonic delay lines have been employed in the past which consist of a solid medium of 5 Fig. 2 is a schematic drawing of a solid delay quartz, glass, or suitable metal in the form of line illustrating one type of echo suppression; a rod or bar with a piezoelectric crystal mounted Fig. 3 is a schematic drawing of a solid delay on either end thereof. An electrical signal, prefline illustrating a second form of echo suppreserably of a frequency of to 30 megacycles, is sion. applied to one of the crystals causing it to vibrate 10 In Fig. l of the drawing there are shown piezomechanically. These vibrations travel down the electric crystals Ill and I2 placed at either end of delay medium until they strike the second crystal. delay medium I4. The second crystal is then set into mechanical Leads I6 electrically connected to crystal Ill vibration and the stresses thus caused in the provide means for applying a signal to or receivcrystal produce an electrical signal that may be ing a signal from this crystal. Leads I3 electritransferred to a suitable receiving device. The cally connected to crystal I2 provides means for received signal is substantially identical to the applying a signal to or receiving a signal from signal applied to the first crystal but is delayed this crystal. For purposes of illustration only by an amount equal to the time of travel of the it will be assumed that a signal will be applied to supersonic energy in the delay medium. crystal I9 and a signal will be received from both In certain types of solid delay lines the energy crystal i2 and crystal I0. The signal received is caused to travel the length of the delay medium by crystal I2 will result from energy traveling several times in order that a longer delay may the length of delay medium dll only once while be obtained with the same physical size of line. the signal received from crystal Ill will result Difliculty is encountered in these delay lines em- 26 from a signal traveling the length of delay meploying multiple reflections due to the fact that dium iii until it reaches crystal I2 and there the beam of energy traveling through the delay being reliected so that it travels the length of medium travels substantially parallel to the axis delay medium It a second time and strikes crystal of the rod but tends to diverge slightly as it pro- I0. gresses and as a result will eventually strike the 3@ The reection at the end of delay medium Ill at boundary or side of the delay medium and rewhich crystal I2 is located may be accomplished bound to the receiving crystal. This is undeby employing a crystal whose acoustical imsirable because the path traveled by this portion pedance is not matched t0 the acoustical iinof the energy striking the boundary of the mepedance of delay medium I4 or it may be acdium is, in general, longer than the path of the complished through the use of suitable reecting energy that does not strike the boundary, thus end cells. In Fig. 1 the primary path of the supernot one but several delayed signals will be resonic energy from crystal IU to crystal I2 will ceived from the delay line. be along the solid line 20, and the primary path of One method heretofore used to eliminate these energy from crystal l2 to crystal I will be along undesired signals is to physically increase the size 4c the solid line 22. Due to the divergence of the of the delay medium so that energy does not strike beam of supersonic energy as it travels through the side or boundary of the medium until after delay medium I 4, secondary paths of energy the desired delay has been attained. The disfrom crystal Iii to crystal I2 will be along the advantage of this solution is that the physical dotted lines 24 and 26. It can be seen from Fig. 1 size and weight of the delay medium must be that energy traveling in paths 24 and 26 will greatly increased. strike the end of delay medium I4 at a slight It is an object of the present invention thereangle with respect to the normal and will, therefore to provide means for suppressing undesired fore, be reflected toward the boundary of delay signals in solid delay lines without increasing medium I4. In this example, energy traveling the physical size of the line. 5c along path 24 rebounds along the dotted path 28 A further object of this invention is to provide Striking the boundary 0f delay medium I4 at aa delay line of small cross section in which ex- IJOrli' 30- At point 30 the energy iS again retraneous echoes are controlled or eliminated. flected and travels along a path 32 to crystal For a better understanding of the invention Ill. In a similar manner energy traveling along together with other and further objects thereof, path 25 Will be reeGted along a path 34 striking 2 reference is had to the following description in which:

Fig. 1 is a schematic drawing of a conventional solid delay line;

atomic crystal it? and displaying the delayed signals on a visual type indicator while adjusting the asymmetry or crystal in. When the desired results have been obtained the adjustment may be made permanent by coating the crystal with paraffin or other similar material or by xing crystal l and electrodes connected to this crystal in any manner well known in the art.

It can be seen that both embodiments of the present invention employ a common operating principle; namely to so direct the path of energy within the transmission medium that energy in the various paths diverging from the normal path and striking the boundary of the medium will be so directed that destructive combination of this energy takes place at the receiving crystal rather than the constructive combination that normally takes place in conventional delay lines.

In other embodiments of the invention, boundary reiiected signals may combine at crystal I2 to form unwanted signals. These signals may be eliminated in exactly the same manner that unwanted signals at crystal lo in this embodiment were eliminated and by either of the methods herein disclosed.

While there has been described what is at present considered the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein Without departing from the invention.

What is claimed is:

1. A delay system comprising a polysurfaced solid delay line having a pair of opposed surfaces and compressional wave transducer means operatively coupled to said surfaces, at least a portion of the surface of said delay line intermediate said surfaces being roughened for attenuating compressional wave components incident thereon.

2. A delay system comprising a polysurfaced solid delay line having a transmitting surface and a receiving surface, a transmitting compressional Wave transducer operatively asssociated with said transmitting surface and a receiving compressional wave transducer operatively associated with said receiving surface, at least a portion of the other surfaces of said delay line being roughened for attenuating compressional wave components incident thereon.

3. A delay system comprising a solid delay line having a transmitting surface and a receiving surface, a transmitting compressional wave transducer operatively associated with said transmitting surface and a receiving compressional wave transducer operatively associated with said receiving surface, the said transducers being asymmetrically disposed relative to each other for attenuating compressional wave components reected from surfaces of said delay line other than said transmitting and receiving surfaces.

4. A delay system comprising a polysurfaced solid delay line having a transmitting surface and a receiving surface, a transmitting compressional wave transducer operatively associated with said transmitting surface and a receiving comn pressional Wave transducer operatively associated with said receiving surface, portions of other surfaces of said delay line being roughened for attenuating compressional wave components re lected from said other surfaces, the said transducers being asymmetrically disposed relative to each other for further attenuating said attenuated components.

5. A compressional-wave delay device comprising a poly-surfaced solid delay line having a pair of opposed surfaces and compression-Wave transducer means operatively coupled to at least one of said opposed surfaces, at least a portion of the surface of said delay line intermediate said opposed surfaces being roughened for the random dispersion of compressional-wave components incident thereon.

6. A compressional wave delay line comprising a solid transmission medium having at least two opposed parallel surfaces, portions of the remaining surfaces of medium being roughened for attenuating compressional wave energy incident thereon, and. compressional Wave transducer means mounted on at least one of said opposed surfaces.

7. A compressional wave delay device comprising a solid compression Wave translating medium having Wave reflecting boundaries, compression wave transducer means coupled to at least one of said boundaries to elect application of compression waves thereto for travel through the medium in a desired direction, at least a portion of said boundaries having deformations to eect a multiplicity of dispersions of the compression waves travelling in other than the desired direction.

8. A delay device according to claim i, wherein said deformations are of the order substantially comparable to the Wave length of said compression waves.

DAVID L. ARENBERG.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,214,595 Rights Sept. 10, 1940 2,263,902 Percival Nov. 25, 1941 OTHER REFERENCES A Textbook of Sound by A. B. Wood, 2 ed., 1941; The Macmillan Co., New York, sec. III, pages 282-285, 301-305, 341-342. 

